/*
    *  Licensed to the Apache Software Foundation (ASF) under one
    *  or more contributor license agreements.  See the NOTICE file
    *  distributed with this work for additional information
    *  regarding copyright ownership.  The ASF licenses this file
    *  to you under the Apache License, Version 2.0 (the
    *  "License"); you may not use this file except in compliance
    *  with the License.  You may obtain a copy of the License at
    *
   *    http://www.apache.org/licenses/LICENSE-2.0
   *
   *  Unless required by applicable law or agreed to in writing,
   *  software distributed under the License is distributed on an
   *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   *  KIND, either express or implied.  See the License for the
   *  specific language governing permissions and limitations
   *  under the License.
   *
   */
  package org.apache.directory.server.ldap.handlers.extended;
  
  
  import java.util.Collections;
  import java.util.HashSet;
  import java.util.Set;
  
  import org.apache.directory.api.ldap.extras.controls.ppolicy.PasswordPolicyRequest;
  import org.apache.directory.api.ldap.extras.extended.pwdModify.PasswordModifyRequest;
  import org.apache.directory.api.ldap.extras.extended.pwdModify.PasswordModifyResponse;
  import org.apache.directory.api.ldap.extras.extended.pwdModify.PasswordModifyResponseImpl;
  import org.apache.directory.api.ldap.model.constants.SchemaConstants;
  import org.apache.directory.api.ldap.model.entry.Attribute;
  import org.apache.directory.api.ldap.model.entry.DefaultAttribute;
  import org.apache.directory.api.ldap.model.entry.DefaultModification;
  import org.apache.directory.api.ldap.model.entry.Entry;
  import org.apache.directory.api.ldap.model.entry.Modification;
  import org.apache.directory.api.ldap.model.entry.ModificationOperation;
  import org.apache.directory.api.ldap.model.entry.Value;
  import org.apache.directory.api.ldap.model.exception.LdapException;
  import org.apache.directory.api.ldap.model.exception.LdapInvalidAttributeValueException;
  import org.apache.directory.api.ldap.model.exception.LdapInvalidDnException;
  import org.apache.directory.api.ldap.model.exception.LdapOperationException;
  import org.apache.directory.api.ldap.model.message.Control;
  import org.apache.directory.api.ldap.model.message.ModifyRequest;
  import org.apache.directory.api.ldap.model.message.ModifyRequestImpl;
  import org.apache.directory.api.ldap.model.message.ResultCodeEnum;
  import org.apache.directory.api.ldap.model.name.Dn;
  import org.apache.directory.api.ldap.model.password.PasswordUtil;
  import org.apache.directory.api.util.Strings;
  import org.apache.directory.server.core.api.CoreSession;
  import org.apache.directory.server.core.api.DirectoryService;
  import org.apache.directory.server.core.api.interceptor.context.BindOperationContext;
  import org.apache.directory.server.core.shared.DefaultCoreSession;
  import org.apache.directory.server.ldap.ExtendedOperationHandler;
  import org.apache.directory.server.ldap.LdapServer;
  import org.apache.directory.server.ldap.LdapSession;
  import org.apache.mina.core.session.IoSession;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  
  /**
   * An handler to manage PwdModifyRequest. Users can send a pwdModify request
   * for their own passwords, or for another people password. Only admin can
   * change someone else password without having to provide the original password.
   *
   * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
   */
  public class PwdModifyHandler implements ExtendedOperationHandler<PasswordModifyRequest, PasswordModifyResponse>
  {
      private static final Logger LOG = LoggerFactory.getLogger( PwdModifyHandler.class );
      public static final Set<String> EXTENSION_OIDS;
  
      static
      {
          Set<String> set = new HashSet<>( 2 );
          set.add( PasswordModifyRequest.EXTENSION_OID );
          set.add( PasswordModifyResponse.EXTENSION_OID );
          EXTENSION_OIDS = Collections.unmodifiableSet( set );
      }
  
  
      /**
       * {@inheritDoc}
       */
      public String getOid()
      {
          return PasswordModifyRequest.EXTENSION_OID;
      }
  
  
      /**
       * Modify the user's credentials.
       * 
       * We will need to modify the userPassword attribute, accordingly to a few rules:
       * - if the old password is present, we should verify it's valid. if not, we return an error
       * - if the old password is absent, we are modifying the password of the current used.
       * - if the new password is absent, we will return an error. The RFC says that we could
       * generate a random password, but that would be dangerous to do so.
      * - if the new password already exists, we simply return not changing anything 
      * - otherwise, we just remove the old password from the list of passwords (we may have 
      * more than one) and add the new password. This is done with a REPLACE operation (Modify)
      */
     private void modifyUserPassword( CoreSession userSession, Entry userEntry, Dn userDn, 
         byte[] oldPassword, byte[] newPassword, PasswordModifyRequest req )
     {
         IoSession ioSession = ( ( DefaultCoreSession ) userSession ).getIoSession();
 
         if ( newPassword == null )
         {
             // We don't support password generation on ApacheDS
             writeResult( ioSession, req, ResultCodeEnum.UNWILLING_TO_PERFORM, 
                 "Cannot change a password for user " + userDn + ", exception : null new password" );
 
             return;
         }
         
         // Get the user password attribute
         Attribute userPassword = userEntry.get( SchemaConstants.USER_PASSWORD_AT );
         
         if ( userPassword == null )
         {
             // We can't modify the password
             writeResult( ioSession, req, ResultCodeEnum.UNWILLING_TO_PERFORM, 
                 "Cannot change a password for user " + userDn + ", the user has no existing password" );
 
             return;
         }
         
         if ( userPassword.contains( newPassword ) )
         {
            // Ok, we are done : just return success
             PasswordModifyResponseImpl pmrl = new PasswordModifyResponseImpl(
                 req.getMessageId(), ResultCodeEnum.SUCCESS );
 
             Control ppolicyControl = req.getControl( PasswordPolicyRequest.OID );
 
             if ( ppolicyControl != null )
             {
                 pmrl.addControl( ppolicyControl );
             }
 
             ioSession.write( pmrl );
 
             return;
         }
         
         if ( oldPassword == null )
         {
             // We are modifying the password on behalf of another user. ACI will
             // protect such modification if it's not allowed. In any case, we just 
             // modify the existing userPassword attribute, adding the password
             ModifyRequest modifyRequest = new ModifyRequestImpl();
             modifyRequest.setName( userDn );
 
             Control ppolicyControl = req.getControl( PasswordPolicyRequest.OID );
             
             if ( ppolicyControl != null )
             {
                 modifyRequest.addControl( ppolicyControl );
             }
             
             try
             {
                 Modification modification = new DefaultModification( ModificationOperation.REPLACE_ATTRIBUTE,
                     userPassword.getAttributeType(), newPassword );
     
                 modifyRequest.addModification( modification );
                 ResultCodeEnum errorCode = null;
                 String errorMessage = null;
 
                 try
                 {
                     userSession.modify( modifyRequest );
 
                     if ( LOG.isDebugEnabled() )
                     {
                         LOG.debug( "Password modified for user {}", userDn );
                     }
 
                     // Ok, all done
                     PasswordModifyResponseImpl pmrl = new PasswordModifyResponseImpl(
                         req.getMessageId(), ResultCodeEnum.SUCCESS );
 
                     ppolicyControl = modifyRequest.getResultResponse().getControl( PasswordPolicyRequest.OID );
 
                     if ( ppolicyControl != null )
                     {
                         pmrl.addControl( ppolicyControl );
                     }
 
                     ioSession.write( pmrl );
 
                     return;
                 }
                 catch ( LdapOperationException loe )
                 {
                     errorCode = loe.getResultCode();
                     errorMessage = loe.getMessage();
                 }
                 catch ( LdapException le )
                 {
                     // this exception means something else must be wrong
                     errorCode = ResultCodeEnum.OTHER;
                     errorMessage = le.getMessage();
                 }
 
                 // We can't modify the password
                 LOG.error( "Cannot modify the password for user {}, exception : {}", userDn, errorMessage );
                 PasswordModifyResponseImpl errorPmrl = new PasswordModifyResponseImpl(
                     req.getMessageId(), errorCode, "Cannot modify the password for user "
                         + userDn + ", exception : " + errorMessage );
 
                 ppolicyControl = modifyRequest.getResultResponse().getControl( PasswordPolicyRequest.OID );
 
                 if ( ppolicyControl != null )
                 {
                     errorPmrl.addControl( ppolicyControl );
                 }
 
                 ioSession.write( errorPmrl );
                 
                 return;
             }
             catch ( LdapInvalidAttributeValueException liave )
             {
                 // Nothing to do, this will never be a problem
             }
         }
         else
         {
             // We are changing the password of the current user, check the password
             boolean valid = false;
             Attribute modifiedPassword = new DefaultAttribute( userPassword.getAttributeType() );
             
             for ( Value value : userPassword )
             {
                 if ( !valid )
                 {
                     valid = PasswordUtil.compareCredentials( oldPassword, value.getBytes() );
                 }
                 
                 try
                 {
                     if ( valid )
                     {
                         modifiedPassword.add( newPassword );
                     }
                     else
                     { 
                         modifiedPassword.add( value );
                     }
                 }
                 catch ( LdapInvalidAttributeValueException e )
                 {
                     // Nothing to do, this will never be a problem
                 }
             }
             
             // At this point, we have what is needed to modify the password, if the oldPassword
             // was valid
             if ( valid )
             {
                 ModifyRequest modifyRequest = new ModifyRequestImpl();
                 modifyRequest.setName( userDn );
 
                 Control ppolicyControl = req.getControl( PasswordPolicyRequest.OID );
                 
                 if ( ppolicyControl != null )
                 {
                     modifyRequest.addControl( ppolicyControl );
                 }
                 
                 Modification modification = new DefaultModification( ModificationOperation.REPLACE_ATTRIBUTE,
                     modifiedPassword );
 
                 modifyRequest.addModification( modification );
 
                 ResultCodeEnum errorCode = null;
                 String errorMessage = null;
 
                 try
                 {
                     userSession.modify( modifyRequest );
 
                     if ( LOG.isDebugEnabled() )
                     {
                         LOG.debug( "Password modified for user {}", userDn );
                     }
 
                     // Ok, all done
                     PasswordModifyResponseImpl pmrl = new PasswordModifyResponseImpl(
                         req.getMessageId(), ResultCodeEnum.SUCCESS );
 
                     ppolicyControl = modifyRequest.getResultResponse().getControl( PasswordPolicyRequest.OID );
 
                     if ( ppolicyControl != null )
                     {
                         pmrl.addControl( ppolicyControl );
                     }
 
                     ioSession.write( pmrl );
 
                     return;
                 }
                 catch ( LdapOperationException loe )
                 {
                     errorCode = loe.getResultCode();
                     errorMessage = loe.getMessage();
                 }
                 catch ( LdapException le )
                 {
                     // this exception means something else must be wrong
                     errorCode = ResultCodeEnum.OTHER;
                     errorMessage = le.getMessage();
                 }
 
                 // We can't modify the password
                 LOG.error( "Cannot modify the password for user {}, exception : {}", userDn, errorMessage );
                 PasswordModifyResponseImpl errorPmrl = new PasswordModifyResponseImpl(
                     req.getMessageId(), errorCode, "Cannot modify the password for user "
                         + userDn + ", exception : " + errorMessage );
 
                 ppolicyControl = modifyRequest.getResultResponse().getControl( PasswordPolicyRequest.OID );
 
                 if ( ppolicyControl != null )
                 {
                     errorPmrl.addControl( ppolicyControl );
                 }
 
                 ioSession.write( errorPmrl );
                 
                 return;
             }
             else
             {
                 // Too bad, the old password is invalid
                 writeResult( ioSession, req, ResultCodeEnum.INVALID_CREDENTIALS, 
                     "Cannot change a password for user " + userDn + ", invalid credentials" );
 
                 return;
             }
         }
     }
 
     
     private void writeResult( LdapSession requestor, PasswordModifyRequest req, ResultCodeEnum error, String errorMessage )
     {
         writeResult( requestor.getIoSession(), req, error, errorMessage );
 
     }
 
     
     private void writeResult( IoSession ioSession, PasswordModifyRequest req, ResultCodeEnum error, String errorMessage )
     {
         LOG.error( errorMessage );
         ioSession.write( new PasswordModifyResponseImpl(
             req.getMessageId(), error, errorMessage ) );
 
     }
     
     
     private Entry getModifiedEntry( LdapSession requestor, PasswordModifyRequest req, Dn entryDn )
     {
         try
         {
             Entry modifiedEntry = requestor.getCoreSession().lookup( entryDn, SchemaConstants.ALL_ATTRIBUTES_ARRAY );
             
             if ( modifiedEntry == null )
             {
                 // The entry does not exist, we can't modify its password
                 writeResult( requestor, req, ResultCodeEnum.NO_SUCH_OBJECT, 
                     "The entry does not exist, we can't modify its password" );
                 return null;
             }
             else
             {
                 return modifiedEntry;
             }
         }
         catch ( Exception le )
         {
             // The entry does not exist, we can't modify its password
             writeResult( requestor, req, ResultCodeEnum.NO_SUCH_OBJECT, 
                 "The entry does not exist, we can't modify its password" );
             return null;
         }
     }
     
     
     private void processAuthenticatedPasswordModify( LdapSession requestor, PasswordModifyRequest req,
         Dn userDn )
     {
         byte[] oldPassword = req.getOldPassword();
         byte[] newPassword = req.getNewPassword();
 
         // We are already bound. Fetch the entry which we want to modify
         Entry modifiedEntry = null;
         
         Dn principalDn = requestor.getCoreSession().getEffectivePrincipal().getDn();
 
         LOG.debug( "User {} trying to modify password of user {}", principalDn, userDn );
         
         
         // First, check that the userDn is null : we can't change the password of someone else
         // except if we are admin
         if ( ( userDn != null ) && ( !userDn.equals( principalDn ) ) )
         {
             // Are we admin ?
             if ( requestor.getCoreSession().isAdministrator() )
             {
                 modifiedEntry = getModifiedEntry( requestor, req, userDn );
                 
                 if ( modifiedEntry == null )
                 {
                     return;
                 }
                 
                 // We are administrator, we can try to modify the user's credentials
                 modifyUserPassword( requestor.getCoreSession(), modifiedEntry, userDn, oldPassword, newPassword, req );
             }
             else
             {
                 // No : error
                 writeResult( requestor, req, ResultCodeEnum.INSUFFICIENT_ACCESS_RIGHTS, 
                     "Non-admin user cannot access another user's password to modify it" );
             }
         }
         else
         {
             // We are trying to modify our own password
             modifiedEntry = getModifiedEntry( requestor, req, principalDn );
 
             if ( modifiedEntry == null )
             {
                 return;
             }
 
             modifyUserPassword( requestor.getCoreSession(), modifiedEntry, principalDn, oldPassword, newPassword, req );
         }
     }
     
 
     /**
      * {@inheritDoc}
      */
     public void handleExtendedOperation( LdapSession requestor, PasswordModifyRequest req ) throws Exception
     {
         LOG.debug( "Password modification requested" );
 
         // Grab the adminSession, we might need it later
         DirectoryService service = requestor.getLdapServer().getDirectoryService();
         CoreSession adminSession = service.getAdminSession();
         String userIdentity = Strings.utf8ToString( req.getUserIdentity() );
         Dn userDn = null;
 
         if ( !Strings.isEmpty( userIdentity ) )
         {
             try
             {
                 userDn = service.getDnFactory().create( userIdentity );
             }
             catch ( LdapInvalidDnException lide )
             {
                 // The userIdentity is not a DN : return with an error code.
                 writeResult( requestor, req, ResultCodeEnum.INVALID_DN_SYNTAX, 
                     "The user DN is invalid : " + userDn );
 
                 return;
             }
         }
 
         byte[] oldPassword = req.getOldPassword();
         byte[] newPassword = req.getNewPassword();
 
         // First check if the user is bound or not
         if ( requestor.isAuthenticated() )
         {
             processAuthenticatedPasswordModify( requestor, req, userDn );
         }
         else
         {
             // The user is not authenticated : we have to use the provided userIdentity
             // and the oldPassword to check if the user is present
             BindOperationContextnterceptor/context/BindOperationContext.html#BindOperationContext">BindOperationContext bindContext = new BindOperationContext( adminSession );
             bindContext.setDn( userDn );
             bindContext.setCredentials( oldPassword );
 
             try
             {
                 service.getOperationManager().bind( bindContext );
             }
             catch ( LdapException le )
             {
                 // We can't bind with the provided information : we thus can't
                 // change the password...
                 requestor.getIoSession().write( new PasswordModifyResponseImpl(
                     req.getMessageId(), ResultCodeEnum.INVALID_CREDENTIALS ) );
 
                 return;
             }
 
             // Ok, we were able to bind using the userIdentity and the password. Let's
             // modify the password now
             modifyUserPassword( requestor.getCoreSession(), bindContext.getEntry(), userDn, oldPassword, newPassword, req );
         }
     }
 
 
     /**
      * {@inheritDoc}
      */
     public Set<String> getExtensionOids()
     {
         return EXTENSION_OIDS;
     }
 
 
     /**
      * {@inheritDoc}
      */
     public void setLdapServer( LdapServer ldapServer )
     {
     }
 }